1. Field of the Invention
This invention relates to the field of lower limb external prosthetics, specifically below-the-knee amputations, such as transtibial and Symes amputations. The invention relates to prosthetics sockets that provide enhanced comfort and control without providing a patellar tendon bar.
2. Related Art
Conventional hard sockets for lower limb external prosthetics, for example, those portrayed in FIGS. 1-5, comprise a patellar-tendon-bar. It should be noted that the patellar-tendon bar (B) may be located at various levels (vertical distances along the socket), depending upon the height and shape of the socket, which in turn is substantially determined by the length and shape of the residual limb. The conventional patellar bars (B) of the prior art sockets in FIGS. 1A and B are located a significant way down the socket from the top edge of the socket, for example, several inches down from the top edge. On the other hand, the conventional patellar bar (B) of FIGS. 2-5 is near the top edge of the socket (formed by approximately the top two inches of the socket in that area).
The patellar-tendon-bar or “patellar bar,” provided in prosthetic “hard sockets” for transtibial or “Symes” amputations, is an inwardly-protruding portion of the socket that contacts and supports the patellar-tendon of the residual limb. This inwardly-protruding portion, though it is traditionally called a “bar” by those of skill in this art, is not literally what most readers would think of as a bar, in that it is not a separate, elongated member installed or imbedded into the socket material. Rather, the bar is a curvature of the socket wall inward into the interior space of the socket in such a location that the wearer's patellar tendon rests on and is supported by the curved socket surface.
While the bar's support of, and impingement against, the patellar tendon in prior art sockets is intended to provide non-bone contact point and support, the inventor believes that this type of support actually leads to discomfort, lack of rotational control, and reduced range of motion. The inventor believes that this type of prior-art support of the weight of the wearer interferes with the tendon during movement in a way that prevents full extension and proper flexion.
The prior art sockets, and also the improved sockets of the invention, may be worn with roll-on liners, including the modern, preferred, roll-on liner with an inner layer of “gel” or other rubbery material and an outer layer of fabric, textile, or other woven material. The preferred embodiments of the invented socket may incorporate various devices for assisting in connecting or holding the socket on the residual limb. For example, a distal lock may be included for anchoring the socket to the roll-on liner, such as are known by those of skill in this field.